Self-assembled monolayers (SAMs) are known in the art. See, for example, Dubois et al., Annu. Rev. Phys. Chem., 1992, 43, p. 437 et seq., which is incorporated herein by reference. Recently, one class of SAM that has received considerable attention are organomercaptans. See, for example, Kim et al. "Polymeric Self-Assembling Monolayer. 1. Synthesis and Characterization of .omega.-Functionalized N-Alkanethiol Containing a Conjugated Diacetylene Group" Tetrahedron Letters, Vol. 35, No. 51, pp. 9501-9504, 1994; Kim et al., "Polymeric Self-Assembling Monolayer. 2. Synthesis and Characterization of Self-Assembled Polydiacetylene Mono- and Multilayers.", J. Am. Chem. Soc., 1995, 117, pp. 3963-3967; and Batchelder et al., "Self-Assembled Monolayer containing Polydiacetylenes", J. Am. Chem. Sc., 1994, 116, pp. 1050-1053, each of which are incorporated herein by reference in their entirety.
One area of study relating to SAMs has involved the stability of such monolayers. While in certain environments, e.g., water or air at room temperature, the SAM's can be considered robust, one disadvantage associated with the use of most SAMs relates to their fragility in environments that involve elevated temperatures and/or solvents able to penetrate the SAM.
One solution to this problem is represented by the polymerization of SAMs. Batchelder et al disclose the use of UV radiation in polymerizing SAMs produced from methyl-terminated diacetylene disulfide. While it has been found that polymerized SAMs have high structural integrity and are more rugged than their unpolymerized counterparts, SAMs produced from methyl-terminated diacetylene disulfide are very limited in their use. Because of the presence of the methyl group at the terminal end of the SAM blocks, the surface of the SAM according to Batchelder is considered nonreactive.
In a different vein, the art has looked at multilayer assemblies of self-assembling monolayers. For example, the formation of built up films by the stepwise adsorption of individual monolayers is described in U.S. Pat. No. 4,539,061 to Sagiv. However, these monolayers suffer from the same disadvantages as other non-polymerized monolayers. Moreover, the process described in this patent itself is limiting. That is, the process requires the use of a molecule having a polar "head" and a non-polar functional group in producing the monolayer. This is followed by a conversion of non-polar groups to a polar head in order to allow for the build up of subsequent monolayers. Accordingly, not only is the disclosed process relatively complex but the practical applications are limited.
Accordingly, the need still exists for an improved polymeric self-assembled mono- and multi-layer structure that does not suffer from the limitations associated with previous films.